How to Tell If You Have Mold in Your Home

Most people think mold is always visible. It's not. A lot of the mold cleanup calls we get in St. John's start with a smell, not a stain. By the time you can see it, it's usually been growing for a while. Here's what to look and smell for.

The most common signs

1. A musty or earthy smell

If a room or a closet smells stale or damp even after you've cleaned it, that's the most reliable early indicator of hidden mold growth. Mold produces volatile organic compounds (VOCs) as it grows, and the smell travels well before the visible colonies do. Basements, crawl spaces, and attics in St. John's homes are the most common sources. If you notice the smell getting stronger in certain weather or after rain, that's a strong sign moisture is getting in somewhere.

2. Visible staining or discolouration

Mold stains are not always black. They can be green, white, grey, or orange depending on the species and the surface. On drywall you'll often see a fuzzy patch. On wood it can look like a dark watermark that doesn't go away. On grout and caulking in bathrooms it tends to show up as black or dark grey streaks. If you're wiping something down and the stain comes back within a week or two, that's mold, not just dirt.

3. Unexplained health symptoms

Mold spores affect people differently. Some people have no reaction at all. Others get persistent nasal congestion, throat irritation, coughing, or skin rashes that don't respond to normal treatment. If symptoms improve when you leave the house and return when you come back, indoor mold contamination is worth ruling out with a proper mold inspection. This is especially true for kids and anyone with asthma or a compromised immune system.

4. Past water damage or leaks

Any time water has gotten in somewhere, mold is a real possibility. A leak that was "fixed" doesn't mean the damp materials dried out completely. Mold can establish itself inside walls, under flooring, or in insulation that looks fine from the outside. If your home has had a roof leak, a burst pipe, flooding in the basement, or a plumbing issue in the last few years, a mold assessment is worth doing even if you can't see or smell anything obvious.

5. Peeling paint or warped walls

Paint that bubbles, peels, or cracks without an obvious cause is often a sign of moisture behind the surface. And where there's persistent moisture, mold cleanup is usually not far behind. Same goes for drywall that feels soft or spongy to the touch, or walls that look like they're bowing slightly outward.

Where to check first

In St. John's homes, the highest-risk areas are:

• Attic — especially if bath fans or range hoods vent into the attic rather than outside
• Basement and crawl space — concrete holds moisture, and older homes often lack proper vapour barriers
• Bathroom walls and ceilings — steam and poor ventilation are a constant problem
• Around windows — condensation and drafts create wet spots that are easy to miss
• Under sinks and around appliances — slow drips go unnoticed for months

When to stop guessing and call someone

If you can smell mold but can't find it, or if you've found a patch larger than about a foot across, it's time to bring in a professional mold inspector. DIY mold testing kits exist, but they're not reliable and won't tell you where the mold is coming from or how far it's spread.

Our team does proper mold inspections in St. John's and across the Avalon Peninsula. We use moisture meters, thermal imaging, and air sampling where appropriate, and we give you a straight answer on what you're dealing with and what needs to happen next.